Hi again, about: int Mac::command(int argc, const char*const argv) why are the lines: else if (strmcp(argv[1], "up-target") == 0) { // code } else if (strmcp(argv[1], "down-target") == 0){ // code } commented? And where do the up-target and down-target come from in void Mac::sendUp(Packet* p) and void Mac::sendDown(Packet* p)? thank you all, Tarik